Processes for the preparation of olefins are known in the art.
U.S. Pat. No. 6,797,851 describes a process for making ethylene and propylene from an oxygenate feed using two or more zeolite catalysts.
In a first stage, an oxygenate feed is contacted with a first zeolite catalyst containing ZSM-5. The resulting conversion product contains an olefins composition. The olefin composition from the conversion reaction, with or without prior separation of ethylene and propylene, is then contacted with another zeolite catalyst in a second stage. The catalyst of such second stage is a one-dimensional zeolite having 10-membered ring channels, including ZSM-22, ZSM-23, ZSM-35, ZSM-42 or mixtures thereof. The eventual product comprises ethylene, propylene and C4+ olefins. The C4+ olefins may be partly recycled to the first stage as olefinic co-feed of the oxygenate feed.
In such an oxygenate-to-olefins (OTO) process carbonaceous material (coke) will deposit on the catalysts used. As a result the catalysts will deactivate in the course of the process with time, and the catalysts need to be regenerated in order to at least partly remove coke formed on the catalysts. During the regeneration, coke is removed from the catalyst. The extent to which coke is removed from the catalyst is an important feature of the process. If insufficient coke is removed, the selectivity of the oxygenate conversion is affected. However, exposing the catalyst to conditions that remove more coke may lead to an undesired reduction of the catalyst activity. Since the activity, selectivity and life time of a catalyst have a considerable impact on the efficiency and cost-effectiveness of an OTO-process, it would be desirable to have a regeneration process that can contribute significantly to the overall performance of an OTO process.